Insulin plays an important role in the overall regulation
of protein synthesis. Protein synthesis (mRNA translation) is conventionally divided into
three stages: initiation, elongation and termination. Both initiation and elongation can
be controlled by Insulin.

The activation of protein synthesis by Insulin is
mediated primarily through Phosphoinositide 3-kinase (PI3K).
This involves the activation of v-akt murine thymoma viral oncogene homolog 1
(AKT(PKB)) where AKT(PKB)
phosphorylates and inactivates Glycogen synthase kinase 3 beta (GSK3
beta), which in turn phosphorylates and inhibits subunit of
eIF2B complex - Eukaryotic translation initiation factor 2B,
subunit 5 epsilon, 82kDa (eIF2B5). Initiation factor
eIF2B mediates the recycling of Eukaryotic translation
initiation factor 2 (eIF2); a major player in recruiting of
the initiator Met-tRNA to the ribosome. eIF2 is active when
bound with GTP and forms a eIF2-GTP-Met-tRNA complex, which binds to the 40S ribosomal
subunit. eIF2B acts by promoting the release of GDP from
eIF2, thus allowing it to be replaced by GTP, to regenerate
the active eIF2-GTP complex. Since
eIF2 is required for every initiation event, modulating the
activity of eIF2B provides a mechanism for controlling
overall rates of peptide-chain initiation [2], [3].

The principal mechanism utilized in the regulation of
eIF4E activity is through its interaction with a family of
binding/repressor proteins termed 4E-BP1. The binding of
4E-BP1 to eIF4E prevents the
interaction of eIF4E with eIF4G1/3
which then suppresses the formation of the
eIF-4F complex. The ability of
4E-BP1 to interact with eIF4E
is controlled via the phosphorylation of
4E-BP1 [4].

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